включение или отключение источников событий (enable or disable event sources)
Имя (Name)
sd_event_source_set_enabled, sd_event_source_get_enabled,
SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT - Enable or disable
event sources
Синопсис (Synopsis)
#include <systemd/sd-event.h>
enum {
SD_EVENT_OFF = 0,
SD_EVENT_ON = 1,
SD_EVENT_ONESHOT = -1,
};
int sd_event_source_set_enabled(sd_event_source *source,
int enabled);
int sd_event_source_get_enabled(sd_event_source *source,
int *enabled);
Описание (Description)
sd_event_source_set_enabled() may be used to enable or disable
the event source object specified as source. The enabled
parameter takes one of SD_EVENT_ON (to enable), SD_EVENT_OFF (to
disable) or SD_EVENT_ONESHOT. If invoked with SD_EVENT_ONESHOT
the event source will be enabled but automatically reset to
SD_EVENT_OFF after the event source was dispatched once.
Event sources that are disabled will not result in event loop
wakeups and will not be dispatched, until they are enabled again.
sd_event_source_get_enabled() may be used to query whether the
event source object source is currently enabled or not. It
returns the enablement state (one of SD_EVENT_ON, SD_EVENT_OFF,
SD_EVENT_ONESHOT) in enabled, if it is not NULL. It also returns
true if the event source is not disabled.
Event source objects are enabled when they are first created with
calls such as sd_event_add_io(3), sd_event_add_time(3). However,
depending on the event source type they are enabled continuously
(SD_EVENT_ON) or only for a single invocation of the event source
handler (SD_EVENT_ONESHOT). For details see the respective manual
pages.
As event source objects stay active and may be dispatched as long
as there is at least one reference to them, in many cases it is a
good idea to combine a call to sd_event_source_unref(3) with a
prior call to sd_event_source_set_enabled() with SD_EVENT_OFF, to
ensure the event source is not dispatched again until all other
remaining references are dropped.
Возвращаемое значение (Return value)
On success, sd_event_source_set_enabled() returns a non-negative
integer. sd_event_source_get_enabled() returns zero if the
source is disabled (SD_EVENT_OFF) and a positive integer
otherwise. On failure, they return a negative errno-style error
code.
Errors
Returned errors may indicate the following problems:
-EINVAL
source is not a valid pointer to an sd_event_source object.
-ENOMEM
Not enough memory.
-ECHILD
The event loop has been created in a different process.
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (See also)
sd-event(3), sd_event_add_io(3), sd_event_add_time(3),
sd_event_add_signal(3), sd_event_add_child(3),
sd_event_add_inotify(3), sd_event_add_defer(3),
sd_event_source_unref(3), sd_event_source_set_ratelimit(3)
